Chromium tripositive

The compounds also illustrate the very great tendency of tripositive chromium to form complexes, which are usually of the octahedral form [CrXf,], for example [CrlNHj) ], [Cr(NH3)5N02] [Cr(CN),] -. 

TRIS(0-ETHYL DITHIOCARBONATO) COMPLEXES OF TRIPOSITIVE CHROMIUM, INDIUM, AND COBALT... 

Tris(0-ethyl dithiocarbonato)chromium(III) is obtained as a dark blue crystalline powder which decomposes at 100 to 140°. The indium(III) ethylxanthate complex forms small colorless crystals which decompose at 130 to 150°.16,17 The cobalt (III) ethylxanthate complex is isolated as a dark green crystalline powder whose decomposition temperature determined by use of a thermal balance is 135 to 137° (lit. value, 117° 2 118 to 119°8). These compounds decompose slowly in air and more rapidly when heated in solution. The tripositive chromium, indium, and cobalt complexes are insoluble in water but are soluble in many organic solvents (Table T). 

A drawback of the simple superacid mechanism is that it implies no particular specificity for manganese (III) any other tripositive cation which readily complexes with peractic acid should be a good catalyst for the reaction. Preliminary experiments with chromium (III), aluminum-(III), and boron (III) acetates indicate that none of these salts catalyzes... 

The magnetic method cannot be applied to tripositive chromium, the structures of the two extreme types having the same number of unpaired electrons and entering into resonance with each other. The chemical properties of the chromium complexes indicate that chromium, like the other iron-group elements, forms hyperligating bonds... 

The efficiency of the electrolytic oxidation is limited to some extent by the reduction of chlorate at the cathode. To check this reduction as far as possible, a little chromate or dichromate is added to the bath. This is partially reduced at the cathode to tripositive chromium, which forms a coating of a chromic chromate around the cathode and thus inhibits the cathodic reduction of chlorate or hypochlorite. 

Perhaps the most striking feature of the complexes described in this section is the great variety of the structural types exhibited. Co-ordination numbers of the metal atoms vary from three to eight, and a wide range of different co-ordination polyhedra is thereby displayed. With one exception, the inorganic complexes of chromium have the metal atom in the tripositive state, but for molybdenum and tungsten the higher oxidation states, from three- to six-positive, are all well represented. Comparative studies of related molecules are few. 

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